单项选择题
A.6m B.5m C.4m D.3m
A.500~1000mm B.800~1200mm C.500~1200mm D.800~1500mm
A.柱箍 B.木框 C.盖板 D.拉紧螺栓
A.75% B.80% C.85% D.90%
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